Hydrolysis with sodium hydroxide of chlorobenzene is a well known method for synthesizing phenol. The reaction is carried out at 360.degree.-390.degree. C. (at 280-300 bar) and each mole of chlorobenzene requires at least two moles of NaOH; small amounts of copper acetate can accelerate the reaction rate. Na phenoxide is formed and pure phenol can be recovered by using an acid; selectivity to phenol approximates 90%. Efforts were already made for converting iodobenzene into phenol, in one or more steps, but the methods followed until now were not satisfactory and another ground which hindered a wide use of aryliodides was the lack of a simple and feasible method for their manufacture; this obstacle was overcome however from the process disclosed by Italian patent publications Nos. 23004 A/84 and 23169 A/84, in the name of the applicant, consisting of a gas-phase synthesis, according to the equation: EQU 2C.sub.6 H.sub.6 +I.sub.2 +1/2O.sub.2 .fwdarw.2C.sub.6 H.sub.5 I+H.sub.2 O
Iodine conversion can be 100% and selectivity to iodobenzene can reach a 98-99% level.
It was now found that conversion of iodobenzene to phenol can be carried out in a very satisfactory way, by means of a process allowing the use of only one equivalent of base per mole of iodobenzene and to recover phenol in a much easier way. A huge advantage, moreover, with respect to the synthesis from chlorobenzene, is the possibility of carrying out the hydrolysis under less drastic operative conditions, especially in terms of temperature and pressure.